Electronic calculator systems of the type wherein all of the main electronic functions are integrated in a single large-scale-integrated semiconductor chip, or a small number of chips, are described in the following prior applications which are assigned to the assignee of this invention:
U.S. Ser. No. 317,493, filed Dec. 21, 1972 (originally filed Sept. 29, 1967, U.S. Ser. No. 671,777) by Jack S. Kilby et al; for "Miniature Electronic Calculator", now U.S Pat. No. 3,819,921 issued June 25, 1974.
U.S. Ser. No. 163,565, filed July 19, 1971, by Gary W. Boone and Michael J. Cochran, for "Variable Function Programmed Calculator" abandoned, continuation filed Dec. 3, 1973 as U.S. Ser. No. 429,999.
U.S. Ser. No. 255,856, filed May 22, 1972, by Michael J. Cochran and Jerry L. Vandierendonck, for "Electronic Calculator", now abandoned, continuation filed Feb. 20, 1974 as U.S. Ser. No. 444,226.
The concepts of these prior applications have made possible vast reductions in cost of small personal sized calculators. Continuing efforts to reduce the cost of these products include reducing the power drain so that the battery requirements are minimized and incorporating more of the external circuits into the semiconductor chip, as well as making the chip more versatile for performing different functions with a minimum change in the manufacturing steps. The purpose of the system of this application is generally related to lowering the power used by a calculator chip, simplifying the system to save space on the chip to facilitate manufacture, simplify programming, incorporate more of the functions such as clock generators and segment drivers into the chip, and/or provide improved functions from a user's standpoint.